The only advantage of a European handset would be that it would support all European 4G (LTE) frequencies (your Galaxy Mega actually supports two out of 5 or so LTE frequency bands used in Europe, however none of the ones currently used in Germany).
However in Germany no operator execpt for eplus allows prepaid subscribers onto their 4G network. Further to that eplus' 4G coverage is still insignificantly small so it does not really makes sense to buy a new phone just to have 4G coverage for a couple of minutes once a day.
4G is a really nice new technology but there is no use of the huge bandwidths from an individual subscriber's point of view because existing 3G networks already do deliver decent data rates that are sufficient for most of us. Of course if you start watching YouTube videos in HD (which makes little sense on a small handheld screen), you may hit the wall, but I still don't see any reasonable mobile application that would need more than let's say 2-3 MBit/s of bandwidth which you can already get through 3G. So while operators try to sell us 4G with 150 MBit/s and more as a beneficial and expensive feature, the real use of 4G is that it relieves capacity constraints on the network and so rather helps operators than subscribers (increased spectral efficency enables better use of assigned frequency spectrum).
An interesting article on this topic comparing European and US networks can be found at:
http://mobilesociety.typepad.com/mob...in-europe.html
4G also has a significant flaw in its inability to place simple voice calls. Because the industry couldn't agree for years how to transmit voice calls via 4G the underlying standard (VoLTE for Voice over LTE) has only been specified at a very late stage when the first 4G networks were already in operation. That is why today's 4G phones need to quickly switch back to 2G or 3G once a call comes in or you place one (called CSFB for circuit-switched fall back) and this does not always work as it should.
I for my part have opted not to buy a 4G phone before they are finally VoLTE capable and before operators have realized that they can't sell 4G at the premium they demand today.